The present invention relates to the field of construction of micro-electro mechanical systems (MEMS) devices and in particular, to the construction of fluid ejection devices in inkjet printheads.
MEMS devices having both mechanical and electrical operation are most often constructed through the utilization of semi-conductor fabrication techniques. Where a mechanical and electrical device is required, the electrical portions can be fabricated utilizing a standard semi-conductor process such as a CMOS (complimentary metal oxide) process or NMOS or BiCMOS process etc. Once the electrical portions are constructed, the mechanical device can then be constructed on top of the CMOS layer through the deposition of a number of layers including sacrificial layers which are utilized together to build up a structure with the sacrificial layer being subsequently etched away so as to release a device for micro-mechanical operation.
The utilization of semi-conductor fabrication techniques can be highly expensive and, where an extremely large number of MEMS devices are to be constructed, it is desirable to limit the expense of construction. The expense of construction is somewhat proportional to the number of independent processing steps which in turn, is often proportional to the number of xe2x80x9cmaskingxe2x80x9d steps utilized in the fabrication process. A masking step is the utilization of a mask so as to delineate an area on a wafer which is to receive specialized processing in contrast with surrounding areas. Ideally, the number of mask steps is minimized.
It is an object of the present invention to provide for the effective utilization of each masking layer in the construction of a micro-electro mechanical system such as an inkjet printhead or the like.
In accordance with a first aspect of the present invention, there is provided a method of forming an inkjet printhead on a substrate said method including:
forming electrical drive circuitry made up of one or more interleaved layers of conductive, semi-conductive and non-conductive materials on a first substrate for the control of said inkjet printhead;
forming on said substrate at least one nozzle chamber having an ink ejection aperture in one wall thereof;
forming a moveable ink ejection paddle within said nozzle chamber, so that the paddle is moveable under the control of an actuator for the ejection of ink out of said ink ejection aperture; and
utilizing portions of at least one of said interleaved layers as sacrificial material in the formation of one or more of the group comprising said actuator and said ink ejection paddle.
The sacrificial material can comprise portions of a conductive layer of the electrical drive circuitry. The electrical drive circuitry can comprise a Complementary Metal Oxide (CMOS) process circuitry and the sacrificial material layer can comprise a CMOS metal layer.
The sacrificial material layer can be used when forming the actuator. The actuator can comprise a thermal actuator. The actuator can be located externally with respect to the nozzle chamber and can be interconnected to the ink ejection paddle through an actuation interconnection aperture formed in a second wall of the nozzle chamber.